Pain can be broadly classified into nociceptive and neuropathic pain. In nociceptive pain, a stimulus of inflammation or tissue damage triggers pain, signaling from the nerve endings. It may be superficial somatic pain, which is easily localized and more likely to be sharp; deep somatic pain, which is also easily localized but in the deeper structures such as bone; and finally, deep, visceral pain that is poorly localized over the organs and more likely to be an ache. Neuropathic pain originates from damage to the nerves themselves, and is characterized by burning, deep aching, tingling, numbness or extremely sharp jabbing pains. These are classified into central, peripheral and mixed types.
Central Neuropathic Pain
Central neuropathic pain is caused by damage to the central nervous system, which includes the spinal cord and brain. Damage to a structure called the thalamus can cause thalamic pain syndrome, also known as Dejerine-Roussy Syndrome. Damage can stem from strokes, cancer in the thalamus, multiple sclerosis or trauma such as vehicle collisions. Interruption of signaling from the spinal cord can also cause central type pain.
Peripheral Neuropathic Pain
Peripheral nerve pain stems from the nerves outside the spinal cord. There are many causes of peripheral nerve pain, and some include nerve damage from diabetes, viral infections such as herpes, or compression such as carpal tunnel syndrome. In complex regional pain syndrome, burning and aching may be accompanied by skin discoloration, abnormal sweating and altered temperature, according to the Mayo Clinic. It is associated with damage to part of the autonomic nervous system that controls involuntary functions and carries pain fibers. Damage may come from trauma such as surgery or fractures.
Mixed Neuropathic Pain
Mixed neuropathic pain is a combination of central and peripheral nerve pain. Causes can be traced to conditions including infections, metastatic cancer, viral infections, nerve tumors, alcoholism, vitamin deficiencies and others. The exact mechanisms leading from the initial insult to the development of these chronic pain conditions have yet to be fully explained.
